In recent years, rapid advances have been made in digitalization of information. This has led to remarkable efforts to meet with this in the imaging field.
In particular, as symbolized by the digital camera, in the imaging surfaces, film is being taken over by use of a solid imaging device such as a CCD (Charge Coupled Device) or CMOS (Complementary Metal Oxide Semiconductor) sensor in most cases.
An imaging lens device using a CCD or CMOS sensor for the imaging element in this way optically captures the image of an object by the optical system and extracts the image as an electric signal by the imaging element. Other than a digital still camera, this is used in a video camera, a digital video unit, a personal computer, a mobile phone, a personal digital assistant (PDA), an image inspection apparatus, an automatic control use industrial camera, and so on.
FIG. 1 is a view schematically showing the configuration of a general imaging lens device and a state of light beams.
This imaging lens device 1 has an optical system 2 and a CCD or CMOS sensor or other imaging element 3.
The optical system includes object side lenses 21 and 22, a stop 23, and an imaging lens 24 sequentially arranged from the object side (OBJS) toward the imaging element 3 side.
In the imaging lens device 1, as shown in FIG. 1, the best focus surface is made to match with the imaging element surface.
FIG. 2A to FIG. 2C show spot images on a light receiving surface of the imaging element 3 of the imaging lens device 1.
Further, imaging devices using phase plates to regularly disperse the light beams, using digital processing to restore the image, and thereby enabling capture of an image having a deep depth of field and so on have been proposed (see for example Non-patent Documents 1 and 2 and Patent Documents 1 to 5).
Further, an automatic exposure control system of a digital camera performing filtering using a transfer function has been proposed (see for example Patent Document 6).    Non-patent Document 1: “Wavefront Coding; jointly optimized optical and digital imaging systems”, Edward R. Dowski, Jr., Robert H. Cormack, Scott D. Sarama.    Non-patent Document 2: “Wavefront Coding; A modern method of achieving high performance and/or low cost imaging systems”, Edward R. Dowski, Jr., Gregory E. Johnson.    Patent Document 1: U.S. Pat. No. 6,021,005    Patent Document 2: U.S. Pat. No. 6,642,504    Patent Document 3: U.S. Pat. No. 6,525,302    Patent Document 4: U.S. Pat. No. 6,069,738    Patent Document 5: Japanese Patent Publication (A) No. 2003-235794    Patent Document 6: Japanese Patent Publication (A) No. 2004-153497